Articulated main rotor hub with inwardly CF bearing and 3% flapping hinge offset

ABSTRACT

A rotary system including a grip having an opening forming a first bridge for receiving a centrifugal force bearing that faces inwardly towards the rotor mast. A rotor blade couples to the grip and a pitch horn positioned outside the opening pitches the rotor blade during flight. A bearing assembly attaches the first bridge to the yoke and controls blade forces exerted against the hub assembly during flight.

BACKGROUND

1. Field of the Invention

The present application relates generally to the field of rotarysystems, and more particularly, to a rotary system having an inwardlyfacing CF bearing assembly.

2. Description of Related Art

Rotary systems are well known in the art for effectively utilizing aplurality of rotor blades to create horizontal and vertical flight.During operation, the rotor blades exert forces, for example, lead/lag,feathering, centrifugal, coning, and/or flapping forces, on the hubassembly, which could result in the rotary system failing. For thisreason, the rotary system will typically utilize one or more differenttypes of devices that compensate for these forces. In some embodiments,the rotary system could include elastomeric elements, spring-ratedampers, bearings, and/or other suitable means for reducing, and in somecases eliminating, the effects of these forces on the hub assembly.

Conventional rotary systems also comprise one or more different devicesfor manipulating movement of the rotor blade during flight, for example,a centrifugal force bearing facing outwardly.

Although great strides have been made in the field of rotary systems,many shortcomings remain.

DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. However, the invention itself, as well asa preferred mode of use, and further objectives and advantages thereof,will best be understood by reference to the following detaileddescription when read in conjunction with the accompanying drawings,wherein:

FIG. 1 is a side view of a rotary aircraft utilizing a rotary system ofthe present application;

FIG. 2 is an oblique view of a tiltrotor aircraft utilizing the rotarysystem of the present application;

FIG. 3 is an oblique view of the rotary system of the presentapplication;

FIG. 4 is an oblique view of a portion of the rotary system of FIG. 3according to the present application; and

FIG. 5 is a cross-sectional view of the rotary system of FIG. 3 taken atV-V of the present application.

While the system and method of the present application is susceptible tovarious modifications and alternative forms, specific embodimentsthereof have been shown by way of example in the drawings and are hereindescribed in detail. It should be understood, however, that thedescription herein of specific embodiments is not intended to limit theinvention to the particular embodiment disclosed, but on the contrary,the intention is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the process of thepresent application as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the rotary system and method are providedbelow. It will of course be appreciated that in the development of anyactual embodiment, numerous implementation-specific decisions will bemade to achieve the developer's specific goals, such as compliance withsystem-related and business-related constraints, which will vary fromone implementation to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time-consuming, but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure.

The rotary system of the present application provides significantadvantageous over conventional rotary systems. Specifically, the rotarysystem utilizes a hub assembly having a bearing assembly, namely, aspherical bearing configured to reduce, and in some cases eliminate, therotor blade forces exerted on the hub assembly during flight. Further,the hub assembly is provided with a pitch horn selectively positionedoutside the yoke, which allows an increase pitch horn longitudinallength and a greater pitching moment exerted on the rotor blade. Theseand other unique features of the rotary system are discussed in detailbelow.

The system and method of the present application will be understood,both as to its structure and operation, from the accompanying drawings,taken in conjunction with the accompanying description. Severalembodiments of the system are presented herein. It should be understoodthat various components, parts, and features of the differentembodiments may be combined together and/or interchanged with oneanother, all of which are within the scope of the present application,even though not all variations and particular embodiments are shown inthe drawings. It should also be understood that the mixing and matchingof features, elements, and/or functions between various embodiments isexpressly contemplated herein so that one of ordinary skill in the artwould appreciate from this disclosure that features, elements, and/orfunctions of one embodiment may be incorporated into another embodimentas appropriate, unless described otherwise.

Referring now to the drawings wherein like reference characters identifycorresponding or similar elements throughout the several views, FIGS. 1and 2 show two different rotary aircraft utilizing the rotary system ofthe present application. FIG. 1 depicts a side view of a helicopter 101,while FIG. 2 depicts an oblique view of a tiltrotor aircraft 201.

Helicopter 101 comprises a rotary system 103 carried by a fuselage 105.One or more rotor blades 107 operably associated with rotary system 103provide flight for helicopter 101 and are controlled with a plurality ofcontrollers within fuselage 105. For example, during flight a pilot canmanipulate the cyclic controller 109 for changing the pitch angle ofrotor blades 107 and/or manipulate pedals 111, thus providing vertical,horizontal, and yaw flight movement.

Tiltrotor aircraft 201 includes two or more rotary systems 203 havingrotor blades 205 carried by rotatable nacelles 204. The rotatablenacelles provide means for allowing aircraft 201 to takeoff and landlike a conventional helicopter and for horizontal flight like aconventional fixed wing aircraft. It should be understood that, likehelicopter 101, tiltrotor aircraft 201 is provided with controls, e.g.,cyclic controllers and pedals, carried within fuselage 207 forcontrolling movement of the aircraft.

Referring now to the remaining FIGS. 3-5, various views of a rotarysystem 301 according to the preferred embodiment of the presentapplication are shown. It will be appreciated that rotary system 301provides effective means for controlling flight of a rotary aircraft,and is provided with one or more unique systems and devices forcompensating rotor blade forces exerted against the hub assembly duringflight. It should be understood that both rotary systems 103 and 203discussed herein comprise one or more of the features of rotary system301. Thus, the features of rotary system 301 are incorporated in rotarysystems for helicopters, tilt rotor aircraft, and other types of rotaryaircraft. It should be apparent that the systems described herein couldbe implemented on a main rotor and a tail rotor as required.

Referring specifically to FIG. 3 in the drawings, rotary system 301comprises a plurality of rotor blades 303 operably associated with a hubassembly 305. During operation, an aircraft engine (not shown) drivesand rotates hub assembly 305 that in turn creates aircraft flight viarotor blades 303. In the exemplary embodiment, rotary system 301 isshown having four rotor blades 303; however, it will be appreciated thatthe features of rotary system 301 could easily be adapted for use withmore or less rotor blades, depending on the desired embodiment. For easeof description, one of the four blades 303 and devices operablyassociated therewith are discussed in detail. However, it should beunderstood that the remaining three blades and operably associateddevices are substantially similar in form and function to blade 303 andinclude the features discussed herein.

Hub assembly 305 comprises a yoke 311 rigidly attached to a rotor mast313 by a chalice. Yoke 311 preferably has an upper plate 315 and a lowerplate 317 coupled together by the chalice. During operation, mast 313rotates yoke 311, which in turn rotates blades 303 attached thereto.Blade 303 attaches to yoke 311 via a grip member 319.

Hub assembly 305 preferably comprises a swashplate (not shown) operablyassociated with yoke 311. Swashplate controls pivoting movement ofblades 303 during flight, in particular, swashplate pivotally attachesto pitch horn 327 via a pitch link 329, and manipulates the pitch angleof rotor blade 303 during flight via pitch horn 327. In the preferredembodiment, pitch horn 327 has a longitudinal length that extends in adirection relatively tangential to the longitudinal length of blade 303.

In some embodiments, a greater pitch horn length is desired to increasethe pitching moment exerted on the rotor blades. For example, in someembodiments large, heavier rotor blades are utilized to increase theaircraft lifting capacity. As the blade size increases, the requiredpitching moment also increases. Having the pitch horn disposed withinthe yoke opening is limited to the yoke dimensions, while on the otherhand, the preferred embodiment of the present application allows for anarm length greater than the dimensions defined by the yoke opening.

Blade grip 319 includes a thickness allowing opening 323 to form a firstbridge 333 for securing grip 319 to yoke 311. In the preferredembodiment, a bearing assembly 353 is utilized to secure grip 319 toyoke 311 via first bridge 333 and the bearing assembly 353 is configuredto control the blade forces exerted against yoke 311. In the exemplaryembodiment, rotor blade 303 is attached to yoke 311 via first bridge 333and with a lead/lag damper 363, which pivotally attaches directly toyoke 311 and grip 319. It will be appreciated that the dimensionallength, thickness, and width of first bridge 333 can easily be modifiedin different embodiments to accommodate different loads exertedthereagainst via the rotor blades 303 during flight. Located interior tothe opening 323 is a second bridge 337 that spans from one edge of thegrip 319 to the opposite edge of the grip 319 across the opening 323.Second bridge 337 includes a stop 339 facing inwards towards the rotormast 313. Stop 339 is typically formed of a metallic compound capable ofproviding a rest for the grip 311 during periods of low centrifugalforce.

In FIGS. 4 and 5, respective perspective cross-sectional and simplifiedside cross-sectional views of a portion of hub assembly 305 are shown.FIG. 5 has some elements removed to simplify the drawing.

Bearing assembly 353 preferably comprises first bearing 369 configuredto elastically attach yoke 311 to an inner surface of first bridge 333.In the preferred embodiment, bearing 369 is composed of an elastomericmaterial that allows for elastic deformation as blade 303 moves relativeto yoke 311. Further description and illustration of these features areprovided below.

Coning stop 373 is configured to provide support to an opposing inwardlyfacing surface of grip 319. As discussed, grip 319 is supported viaconing stop 373 during periods of low centrifugal force on the rotorsystem 305. In the preferred embodiment, coning stop 373 compensates forblade flapping during startup and shut down of the rotor system 305.Yoke 311 includes an attachment means 377 extending from yoke 311 thatis utilized to fit within a hole of coning stop 373. Attachment means377 is preferably a circular shaft having a diameter substantially equalto the inner diameter of hole. Coning stop 373 includes a first member379, and a second member 381 rigidly attached to first member 379 attypically a right angle. First member 379 is weighted such that attypical operating speeds, the centrifugal force of the spinning rotorsystem 305 forces second member 381 to rotate into a more verticalposition such that the grip 319 is unsupported by coning stop 373. Asthe rotor system 305 slows down and the centrifugal force exerted on thefirst member 379 is decreased, the second member 381 rotates outward andprovides resting support for grip 319 against stop 339 located in thesecond bridge 337.

Bearing 369 includes an inner member 387, an outer member 391, and anelastomeric portion 393, and is preferably a lensed sphericalcentrifugal bearing having a conical profile bounded substantially by apair of coaxial spherical surfaces, the first of which is formed on acorresponding spherical surface 385 of inner member 387, and the secondof which is formed on a corresponding spherical surface 389 of an outermember 391 fixedly attached to yoke 311. Having the conical profilepoint inwardly forces the inner member 387 to be narrower than the outermember 391. Outer member 391 or the first end portion of the bearing 369rigidly connects bearing 369 to yoke 311. Inner member 387 or the secondend portion of the bearing 369 is rigidly coupled to the grip 319 andpivots with the grip 319. Inner member 387 is mechanically coupled tothe outer member 391 by the elastomeric portion 393. Inner member 387received centrifugal compression forces from the grip 319 along alongitudinal bearing axis; furthermore, the inner member 387 rotatesrelative to the outer member 391 about the longitudinal bearing axis.The apex of the conical profile of bearing 369 is positioned towards thecenter of the rotor system, for example the rotor mast 313. Bearing 369includes a focal center positioned towards the rotor mast 313 and thecenter of the yoke 311 and therefore is inwardly facing. Additionally,the focal center of the bearing 369 is preferably located at the sameblade station as the center of the pivot attachment between the lead/lagdamper 363 and the yoke 311.

The two members to which the spherical surfaces of bearing 369 arecoupled constitute together with the bearing a single mechanicalelement. In this respect, the connection between the bearing 369 andinner member 387 (by way of surface 385) and between the bearing 369 andouter member 391 (by way of surface 389) is permanent, and is made forexample by vulcanizing the elastomeric material constituting the bearing369 directly on to these surfaces, or alternatively by fixing thematerial in any other non-removable manner to the two members. Bearing369 is preferably provided with a plurality of rigid shims or pliesdisposed and layered therein the elastomeric portion 393.

Rotating the centrifugal force bearing from pointing outwards topointing inwards results in a flapping hinge offset between 2% to 4%,and the delta three of the rotor system remains at approximately 0degrees. Additionally, the inwardly facing centrifugal force bearingreduces loads experienced by the rotor system resulting in reducedweight for an articulated rotor.

It is apparent that a system and method with significant advantages hasbeen described and illustrated. The particular embodiments disclosedabove are illustrative only, as the embodiments may be modified andpracticed in different but equivalent manners apparent to those skilledin the art having the benefit of the teachings herein. It is thereforeevident that the particular embodiments disclosed above may be alteredor modified, and all such variations are considered within the scope andspirit of the application. Accordingly, the protection sought herein isas set forth in the description. Although the present embodiments areshown above, they are not limited to just these embodiments, but areamenable to various changes and modifications without departing from thespirit thereof.

What is claimed is:
 1. A rotary system for a rotary aircraft,comprising: a rotor mast; a swashplate rotatably carried by the rotormast; and a hub assembly for securing a rotor blade to the rotor mast,the hub assembly having: a yoke rigidly attached to the rotor mast, theyoke having: an upper plate; and a lower plate; a blade grip forsecuring the rotor blade to the yoke, the grip having: a thickness; andan opening extending through the thickness, the opening forming abridge; wherein the blade grip is operably associated with theswashplate for providing pitching movement of the blade during flight; adamper pivotally attached to the blade grip and the yoke; and a bearingassembly having; a spherical centrifugal bearing having; a conicalprofile bounded substantially by a pair of coaxial spherical surfaces;and a focal center positioned inwardly towards the rotor mast; whereinthe bearing assembly is configured to attach the blade grip to the yoke;and wherein the bearing assembly controls blade forces exerted againstthe hub assembly during flight.
 2. The rotary system of claim 1, whereinthe spherical centrifugal bearing is composed of elastomeric material.3. The rotary system of claim 1, wherein the focal center of thespherical centrifugal bearing is located at a first distance from therotor mast; and wherein a center of the pivotal attachment between thedamper and the yoke is located the first distance from the rotor mast.4. The rotary system of claim 1, wherein an apex of the sphericalcentrifugal bearing is positioned towards the rotor mast.
 5. The rotarysystem of claim 1, wherein the spherical centrifugal bearing isasymmetrical shaped.
 6. The rotary system of claim 2, further comprisinga coning stop.
 7. The rotary system of claim 6, the coning stop having:a weighed first member; and a second member; wherein the blade griprests on the second member during periods of low centrifugal forceexerted on the rotary system.
 8. The rotary system of claim 1, whereinan apex of the spherical centrifugal bearing faces the bridge.
 9. Arotary system for a rotary aircraft, comprising: a yoke; a grip havingan opening forming a bridge and rigidly attached to a rotor blade; and abearing assembly having a spherical centrifugal bearing having a conicalprofile bounded substantially by a pair of coaxial spherical surfaces;wherein a diameter of the spherical centrifugal bearing is the smallestclosest to an axis of rotation of the yoke; wherein the bearing assemblyis operably associated with the grip, the bearing assembly beingconfigured to attach the grip to the yoke; wherein the bearing assemblycontrols blade forces exerted against a hub assembly during flight; andwherein a focal center of the spherical centrifugal bearing ispositioned towards a center of the yoke.
 10. The rotary system of claim9, the yoke comprising: an upper plate; and a lower plate.
 11. Therotary system of claim 10, further comprising: a coning stop.
 12. Therotary system of claim 9, wherein the spherical centrifugal bearing islocated within the opening of the grip.
 13. The rotary system of claim9, further comprising: a damper pivotally connecting the yoke to thegrip; wherein a focal center of bearing assembly is located at a bladestation equal to a blade station of a center of the pivotal attachmentbetween the damper and the yoke.